The present invention is generally directed to barcode scanners which are useful for reading barcodes on surfaces which exhibit different reflectivities. More particularly, the present invention is directed to a bar code scanner employing a broad spectrum light source of adjustable intensity which is made to vary in order to accommodate different surfaces on which the barcode is disposed.
There is a need in the barcode scanning or reading area to improve readability with respect to barcodes placed on a variety of different surfaces. Such surfaces include silicon semiconductor wafers, magneto restrictive disk drive elements, polymeric materials employed in the manufacture of CD ROM disks, glass, such as that used in the manufacture of cathode ray tubes, and various forms of plastic material. In particular, there is a need to be able to read barcodes disposed on surface structures which have different reflectivities. For example, the surface of a semiconductor wafer may have different colors when it has gone through various chemical processes such as alkaline and acid etchings. These colors can affect reflectivity and readability of barcodes placed thereon by laser etching.
Barcode scanners which use a CCD camera and employ lasers as light sources, such as those typically seen in a supermarket checkout counter, are however not capable of reading barcodes placed on materials having a wide range of reflectivities. Nonetheless it is very desirable to place barcode information on such surfaces. Similarly, barcode scanners which employ light emitting diode (LED) devices as the light source, are found not to be optimal for reading barcodes which are present on materials of differing reflectivity. One of the reasons that barcode scanners are unsuccessful with such materials is that the intensity of the light from the light source is fixed and is not adjusted according to the reflectivity of the material on which the barcode is placed.
It has been discerned by the present inventors that, by providing adjustable aspects to a barcode reader, it is possible to enhance the reliability of barcode reading. In particular, it has been discerned by the present applicants that, when a barcode is written on a surface with a certain reflectivity, it is desirable to vary the intensity of the light source to improve readability. In particular, applicants have also discerned that light intensity should be decreased for highly reflective surfaces and increased for surfaces with low reflectivity.